Ultrasonic diagnostic apparatuses, which are being widely used for diagnosis of organs, blood vessels, and fetuses, have played a significant role in diagnosis of heart conditions, for example. Use of an ultrasonic diagnostic apparatus enables observation of a beating heart, for example, in an ultrasonic moving image.
During ultrasonic diagnosis of heart conditions, fixed echoes (stationary echoes) are generated in an ultrasonic image due to the chest wall, ribs, pericardium, and so on, that are present on a superficial side (toward the probe) with respect to the heart. These stationary echoes cause deterioration of the quality of an ultrasonic image in ultrasonic diagnosis targeted on the heart. There have therefore conventionally been proposed methods of reducing these stationary echoes.
Patent Document 1, for example, proposes technology of applying a high-pass filter (HPF) to frame data obtained by transmitting and receiving ultrasound, along an arrangement direction of a plurality of frames, i.e. applying HPF processing between frames (inter-frame HPF processing), to thereby reduce stationary echoes whose fluctuations concerning the arrangement direction (time direction) of the plurality of frames are smaller than those of the heart.
With the simple inter-frame HPF processing, however, as it is difficult to completely maintain echoes from the heart with only the stationary echoes being completely removed, residual stationary echoes are partially generated, or loss of echoes from the heart occurs, resulting in generation of flicker within the moving image. Further, processing corresponding to weighted summation between a plurality of frames in the inter-frame HPF processing causes a problem that a heart valve or the like which moves at a high speed appears double or triple in the moving image, and also a problem that the borderline of the heart (cardiac muscle) becomes blurred.
Patent Document 2, for example, proposes technology of further performing inter-frame LPF (low-pass filter) processing after the inter-frame HPF processing in order to reduce the flicker described above. In other words, smoothing (flattening) between the frames is performed by the LPF processing to thereby reduce the flicker. This technology, however, suffers from a further problem that the inter-frame LPF processing, when simply performed for a whole image, makes the whole image blurred.
Patent Document 3, for example, proposes technology of increasing the weight of frame data after HPF processing in a superficial region in which a large number of stationary echoes are present and increasing the weight of frame data before the HPF processing in a deep region in which the heart exists, so that weighted summation is applied to frame data before and after the HPF processing, in order to suppress the flicker and blurring described above. With this technology, the stationary echoes are reduced in the superficial region while flicker and blurring relating to the heart are suppressed in the deep region. However, this technology also causes a problem with respect to circuit scale, such as a problem that a circuit structure for applying weighted summation is necessary, for example.